Two-time world champion Giorgia Bronzini (Cylance) was second with UniSA-Australia's Lauretta Hanson third across the line at the end of the 115km stage out and back from Gumeracha.
Earlier in the day Rachel Neylan (UniSA-Australia) launched a solo bid for victory but she was caught two kilometres from home to set up a bunch sprint finish.
Temperatures topped 38 degrees but the Wiggle-Hi5 team handled the heat and the competition to set up Edmondson for the final sprint.
Chloe Hosking (Ale Cipollini) claimed the first intermediate sprint from Edmondson and Em Moberg (Virtue Cycling) but Edmondson's stage win gives her the lead in the sprinter’s competition.
Sabrina Stultiens (Waowdeals) a former under-23 world road race champion leads in the mountains classification.